Brake condition warning switch and system

ABSTRACT

This specification describes a pressure failure indicating device for use with dual hydraulic master cylinders in a vehicle braking system. This system senses a loss of pressure in either of two power chambers to energize a warning lamp in one of the pressures is not up to a predetermined value and also energizes a stop light when pressure in either chamber is up to a predetermined value.

United States Patent Winston et al. 1 May 23, 1972 [54] BRAKE CONDITIONWARNING References Cited SWITCH AND SYSTEM UNITED STATES PATENTS 4 [72]Inventors: John MrWinston, Birmingham; willter H. 1,557,330 10/1925Reynolds .L ..340/52 UK I Zimmerman, Rochester, both of Mich. 2,053,3539/ 1936 Talbot ..340/236 UX 2,203,908 6/1940 Hess... ..60/54.6 E X 1Asslgnw 'P Mum W Dem", 2,332,301 10/1943 Cox ...340/60 ux Mlch-2,979,364 4/1961 Putnam ..340/52 C X [22] Filed: Apr. 17, 1970 3,273,1169/1966 Quiros et al. ..340/60 [21] App]. N0.: 28,240 PrimaryExaminer-John W. Caldwell Assistant Examiner-Kenneth N. Leimer Related0.8. Application Data Attomey-W. E. Finken and D. D. McGraw [63]gsrrlizgmation of Ser. No. 606,945, Jan. 3, 1967, aban- [57] ABSTRACTThis specification describes a pressure failure indicating [521 0.8. CI..340/60, 340/52 B, 340/71 device for use with dual hydraulic mastercylinders in a vehicle [5]] Int. Cl. ..B60g l/44, B60t 17/22 brakingSystem This System Senses a 1055 9f P in either I 58] of two powerchambers to energize a warning lamp in one of Field of Search..200/8l.4, 81.5; 340/52, 59, 340/60, 66, 69, 71, 72; 188/1 A, 151 A thepressures is not up to a predetermined value and also energizes a stoplight when pressure in either chamber is up to a predetermined value.

3 Claim, 3 Drawing figures BRAKE CONDITION WARNING SWITCH AND SYSTEMThis application is a continuation of application Ser. No. 606,945,filed Jan. 3, 1967, now abandoned.

This invention relates to warning systems and more particularly to afluid or pressure loss warning system adapted for use with brakingsystems utilizing a dual master cylinder.

Separate braking systems for use on rear and front wheel brakes of motorvehicles have come into wide usage with the use of a single mastercylinder having separate power producing areas for energizing separatelythe front and rear wheel brakes of a vehicle. This type is generallyknown as a dual master cylinder. Other systems having a similar functionutilize separate master cylinders generally with a single actuator.While these braking systems provide separate. braking for front and rearwheels of a vehicle and a vehicle can therefore be stopped while eitheris functioning, it sometimes is difficult to ascertain whether or notboth braking systems are functioning properly. This is due in part tothe extremely efficient braking systems found on motor vehicles ofrecent vintage as well as by the fact that braking may be accomplishedunder conditions of trafiic when the full capability of even a singlesystem is not utilized to stop the vehicle. It therefore becomesdesirable to have an indicating mechanism which apprises the vehicleoperator of the failure of either braking system when avehicle is soequipped.

It is an object of the present invention to provide an improved brakepressure and fluid loss warning system for a I vehicle having a dualbraking system.

It is another object of the present invention to incorporate a stoplight operating switch into a braking system equipped as described inthe previous object.

It is still another object of the present invention to provide animproved fluid pressure and loss warning system for a dual brakingsystem which is readily adaptable for use with hydraulic mastercylinders of different designs.

It is a further object of the present invention to provide an improvedfluid pressure and loss warning system for a dual braking system whichis readily adaptable to be made integral with a master cylinder.

It is still a further object of the present invention to provide animproved fluid pressure and loss warning system according to theaforementioned object which is simple, reliable, and

economical to manufacture.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein preferred embodiments of the present invention areclearly shown.

IN THE DRAWINGS:

FIG. 1 is a sectional view of one embodiment of the subject inventionshown in its operative environment;

FIG. 2 is a sectional view of another embodiment of the subjectinvention shown in its operative environment;

FIG. 3 is a circuit diagram of the indicating system of FIG. 1.

Referring to FIG. 1, a dual braking system having a dual master cylinderis illustrated in which a force is provided in bore in the direction ofthe arrow which results in power piston 12 and power piston 14 moving inbore 10 to the left, as viewed in FIG. 1, resulting in a pressurebuildup of fluid in chamber I6 and chamber I8. An outlet from chamber 16is common to an inlet to switch body 22 and communicates a pressurethrough chamber 24 and line 26 to brakes carried by wheels 28 and 30 ofa vehicle, not shown.

Chamber 18 has an outlet 32 similar to outlet 20 communicating throughchamber 34 and line 36 to brakes on vehicle wheels 38 and 40. It is seenthat FIG. I depicts a dual master cylinder supplying pressure for a dualbraking system of well known design.

Enclosing one end of chamber 24 is a piston 42 drivably engagingactuator 44. Chamber 34 is similarly closed by piston 46 and actuator48.

A switching chamber 50 is formed in switch body 22. Fixed contacts 52and 54 are formed in a wall of switch body 22 and both are inelectrically conductive relationship with a power source or battery 56through ignition switch 58. Fixed contact 60, also formed in a wall ofswitch body 22, conductively engages stop light 62. Fixed contacts 64and 66 are carried by switch body 22 in opposition to contacts 52 and 54and conductively engage each other through strip 82. In addition, fixedcontact 64 is in electrically conductive engagement with pressurewarning lamp 68. Movable contact 70 is carried at an end of flexiblemember 72 and is operatively disposed between fixed contacts 64 and 52.Movable contact 74 is similarly operatively disposed between fixedcontacts 66 and 54 and is carried by flexible member 72 at an oppositeend from contact 70. Flexible member 72 is mounted on an upraisedportion 76 of switch body 22 and conductively engages fixed contact 60.

When the braking system shown in FIG. I is in a poised or unpressurizedcondition, movable contacts 70 and 74 engage fixed contacts 64 and 66respectively. This is the situation whether or not ignition switch 58 isclosed.

When a force is exerted on piston 12 or 14 in the direction ofthe'arrow, pressure buildup normally occurs in chambers 16 and 18 if thebraking systems are functioning. This pressure is communicated throughoutlets 20 and 32 into chambers 24 and 34, respectively. Pressure issimultaneously communicated through lines 26 and 36 to the vehiclebrakes as well as being operative against pistons 42 and 46. Whenpressure exists in both chambers 24 and 34, actuators 44 and 48 drivecontacts 74 and 70, respectively, carried by flexible member 72 intoengagement with fixed contacts 54 and 52.

With pressure available in the braking system and sensed in the mannerpreviously set forth, contact 74 engages fixed contact 54 and movablecontact 70 engages fixed contact 52. Referring to the circuit diagram ofFIG. 3, assuming ignition switch 58 to be closed, a path for currentflow exists to stop light 62 but not to warning lamp 68. This is thenormal condition of operation when no pressure or fluid loss is beingexperienced in the braking system described.

Assuming that a pressure loss develops in line 26, for example, nopressure will build up in chamber 16 or in chamber 24 when a force isexerted on power piston 12 and, therefore, piston 42 will not actagainst resilient member 72 and contact 74 through actuator 44.Therefore, movable contact 74 remains stationary against fixed contact66. Assuming ignition switch 58 to be closed, a path for current flowexists through lead 80 to fixed contact 52 through movable contact 70,moved into engagement therewith by a pressurized piston 46, throughflexible member 72 to contact 60 and stop light 62. In addition, a pathfor current flow also exists through lead 80, through contact 52 tomoved contact 70 and flexible member 72, through contacts 74 and 66,through conductive connector 82 to contact 64 and lead 84 to warninglamp 68. Therefore, under this condition of operation, when pressuredoes not build up properly in chamber 24, stop light 62 is operative andwarning lamp 68, typically situated in the driving compartment of avehicle, warns a vehicle operator that one of the braking systems hasfailed and maintenance is necessary. An examination of the circuitdiagram of FIG. 3 more clearly sets forth the electrical relationshipsbringing about the aforementioned result.

If a pressure or fluid loss occurs in chamber 18, chamber 34 or line 36,the same sequence of events occurs as described for a pressure loss inline 26 and its associated system resulting in warning lamp 68 and stoplight 62 operating to bring about a warning to a vehicle operator aswell as normal functioning of the stop light. I

Another embodiment of the present invention is illustrated in FIG. 2wherein a sensing switch is illustrated that can be separate from thehydraulic master cylinder and merely needs to be connected betweenbraking lines of separate braking systems to be operative. Referring toFIG. 2, a switch body has an inlet 102 from a braking line 104 of afirst braking system and an inlet 106 from line 108 of a second brakingsystem. The first and second braking systems described herein operate inmuch the same fashion as the braking system fixed contact 120 but ismovable into engagement with a second'fixedcontact 122 under certainconditions of operation. Spring 124 is contained by insulating block 126and acts against actuator 1 16 to keep movable contact 1 18 in conductive relationship with fixed contact 120.

Similar to'the arrangement just described diaphragm 130 is acted upon bythe pressure in inlet 102. A movable strip 132 is carried in a wall ofswitch body 100 and in turn carries the contact 134 in normal engagementwith fixed contact 136. Contact 134 is movable into engagement withanother fixed contact 138 under certain conditions of operation. Spring140 acts'against actuator 142 carried by movable strip 132 and urgescontact 134 toward contact 136. Contact 136 and contact 122 areelectrically connected through lead 144, and contacts 138 and 120 areelectrically connected by lead 146. Pressure or fluid loss warning lamp148 conductively engages strip 112 and battery 150 conductively engagesstrip 132 through ignition switch 152.

Under normal conditions of operation, pressures are built up in lines104 and 108 resulting in a pressure being transmitted to inlets 102 and106. Diaphragms 130 and 110 are acted upon simultaneously drivingcontacts 134 and 118, respectively, into associated contacts 138 and122. Assuming ignition switch 152 to be closed, it is seen that noconductive path exists to lamp 148 because contacts 118 and 120 areseparated.

Assuming a pressure loss in line 108, diaphragm 110 would not move inthe aforementioned sequence of operation resulting in contact 118 and120 remaining engaged. In this case, the conductive path to lamp 148 iscomplete and lamp 148 lights indicating a loss of pressure or fluid.

A similar result is obtained if a loss of pressure exists in line 104which results in diaphragm 130 remaining stationary with contacts 134and 136 remaining engaged. Contact 118, of course, moves into contact122 completing a path for electrical current to lamp 148 by way of lead144 and contact 136,

still engaged by contact 134 and strip 132. Therefore, a pressure lossin either lines 104 or 108 results in the energization of lamp 148. v

It is clear that either embodiment of the subject invention is adaptedfor use as being integral with a master cylinder as. shown in FIG. 1 oras a separate pressure operated switch as shown in FIG. 2. The designerof the particular braking system will determine whether or not theswitches would be integral or separate. Both of the subject embodimentsfind utility as indicators in dual braking systems to apprise a vehicleoperator of a failure in either system. The electrical connections areall external to the master cylinders and, therefore, the invention isvery easily adapted for use with dual braking systems already mounted onthe vehicles as well as being capable of being made integral withdual'braking systems when designed as original equipment on vehicles.

While the embodiments of the invention as herein disclosed constitutepreferred forms, it is to be understood that other forms might beadopted.

What is claimed is as follows:

1. lna vehicle braking system having first and second vehicle brakeactuating circuits and a dual master cylinder including first and secondpressurizing chambers for separately pressurizing said first and secondvehicle brake actuating circuits, a brake circuit condition indicatorcomprising:

first and second pressurizing outlets respectively pressure connectingsaid first and second master cylinder pressurizing chambers to saidfirst and second vehicle brake actuating circuits;

first and second movable pressure responsive members respectivelyconnected with said first and second outlets to receive pressurestherefrom;

a switch housing in which said pressure responsive members are mounted;switch means in said switch housing includ-. mg

a first movable contact actuated by said first pressure responsivemember,

a first'pair of fixed contacts, one of which is engaged by said firstmovable contact when no pressure is received by said first pressureresponsive member, and the other of which I is engaged by said firstmovable contact when at least a predetermined minimum pressure isreceived by said first pressure responsive member,

a second movable contact actuated by said second pressure responsivemember, I

a second pair of fixed contacts, one of which is engaged by said secondmovable contact when no pressure is received by said second pressureresponsive member, and the other of which is engaged by saidsecondmovable contact when at least a predetermined minimum pressure isreceived by said second pressure responsive member;

electrical circuitry including said switch means and a source ofelectrical energy and fluid pressure condition indicating means andelectrical lead means selectively interconnecting said fluid pressurecondition indicating means and said source of electrical energy throughsaid switch means in accordance with the position of said first movablecontact in relation to said first pair of fixed contacts and theposition of said second movable contact in relaenergize said fluidpressure condition indicating means when only one of said first andsecond pressure responsive members receives pressure at or above saidpredetermined minimum pressure to move only one of said movable contactsout of electrical contact with one of said pair of fixed contactsassociated therewith and into electrical contact with the other of saidpair of fixed contacts associated therewith,

the energization of said fluid pressure condition indicating meansinforming the vehicle operator of the condition wherein the lack ofpressure in one of said vehicle brake actuating circuits existsconcurrently with pressure at or above said predetermined minimumpressure in the other of said vehicle brake actuating circuits,

second fluid pressure condition indicating means and second electricallead means connecting the same to said first and second movablecontacts,

said first-named electrical lead means having a portion thereofelectrically connecting said first-named indicating means with said onefixed contacts of said first and second pairs of fixed contacts, andhaving anotherportion thereof electrically connecting said source ofelectrical energy with said other fixed contacts of said first andsecond pairsof fixed contacts,

said second fluid pressure condition indicating means being energized bysaid source of electrical energy through said switch means and saidfirst-named and said secondnamed electrical lead means when pressure ator above said predetermined pressure is received by either or both ofsaid first and second pressure responsive members to move either or bothof said first and second movable contacts into engagement with the otherof said pair of fixed contacts associated therewith,

the energization of said second fluid pressure condition indicatingmeans indicating the condition wherein pressure exists at or above saidpredetermined minimum pressure in at least one of said vehicle brakeactuating circuits.

2. In a brake system having a first fluid circuit and a second fluidcircuit for actuating brakes connected to said circuits, each of saidfluid circuits having a brake system operating condition wherein thefluid circuits are pressurized with brake applying pressure and having abrake released condition in which the circuits are not pressurized,

a brake system pressurization condition warning systemcomprising:

first and second brake system operating condition sensors each includingswitch means opened and closed in accordance with the operatingconditions sensed, said sensors respectively sensing the presence andabsence of the first and second brake circuit pressurization conditions,

first warning means actuated by at least one of said system operatingcondition sensors through said switch means by the presence of brakeactuating pressure in at least one of said fluid circuits and sensed byat least one of said sensors,

and second warning means actuated through a series connection formedthrough said switch means of both said first and second sensors, saidseries connection being established by the presence of the .brake systemoperating condition in one of said circuits and the absence of the brakesystem operating condition in the other circuit as respectively sensedby said first and second sensors when the brake system is activated tooperate the brakes connected to both fluid circuits and one of saidfluid circuits is not pressurized.

3. The brake system condition warning system of claim 2,

said first and second sensor switch means respectively comprising afirst switch and a second switch, each of said first and second switcheshaving:

first and second and third contacts and means biasing said third contactinto engagement with said first contact,

said first and second sensors respectively further including first andsecond pressure responsive means respectively fluid connected with saidfirst and second fluid pressure actuated brake circuits and actuatableupon pressurization of the associated fluid pressure actuated brakecircuit to move said associated third contact from engagement with saidassociated first contact to engagement with said associated secondcontact,

a source of electrical energy and means connecting said second contactsthereto,

means connecting said third contacts to said first warning means,

and means connecting said first contacts to said second warning means.

1. In a vehicle braking system having first and second vehicle brakeactuating circuits and a dual master cylinder including first and secondpressurizing chambers for separately pressurizing said first and secondvehicle brake actuating circuits, a brake circuit condition indicatorcomprising: first and second pressurizing outlets respectively pressureconnecting said first and second master cylinder pressurizing chambersto said first and second vehicle brake actuating circuits; first andsecond movable pressure responsive members respectively connected withsaid first and second outlets to receive pressures therefrom; a switchhousing in which said pressure responsive members are mounted; switchmeans in said switch housing including a first movable contact actuatedby said first pressure responsive member, a first pair of fixedcontacts, one of which is engaged by said first movable contact when nopressure is received by said first pressure responsive member, and theother of which is engaged by said first movable contact when at least apredetermined minimum pressure is received by said first pressureresponsive member, a second movable contact actuated by said secondpressure responsive member, a second pair of fixed contacts, one ofwhich is engaged by said second movable contact when no pressure isreceived by said second pressure responsive member, and the other ofwhich is engaged by said second movable contact when at least apredetermined minimum pressure is received by said second pressureresponsive member; electrical circuitry including said switch means anda source of electrical energy and fluid pressure condition indicatingmeans and electrical lead means selectively interconnecting said fluidpressure condition indicating means and said source of electrical energythrough said switch means in accordance with the position of said firstmovable contact in relation to said first pair of fixed contacts and theposition of said second movable contact in relation to said second pairof fixed contacts, said electrical circuitry being open at said switchmeans when no pressures at or greater than said predetermined minimumpressures are received by said first and second pressure responsivemembers and when pressures at or greater than said predetermined minimumpressures are received by both of said first and second pressureresponsive members, said electrical circuitry being closed at saidswitch means to energize said fluid pressure condition indicating meanswhen only one of said first and second pressure responsive membersreceives pressure at or above said predetermined minimum pressure tomove only one of said movable contacts out of electrical contact withone of said pair of fixed contacts associated therewith and intoelectrical contact with the other of said pair of fixed contactsassociated therewith, the energization of saId fluid pressure conditionindicating means informing the vehicle operator of the condition whereinthe lack of pressure in one of said vehicle brake actuating circuitsexists concurrently with pressure at or above said predetermined minimumpressure in the other of said vehicle brake actuating circuits, secondfluid pressure condition indicating means and second electrical leadmeans connecting the same to said first and second movable contacts,said first-named electrical lead means having a portion thereofelectrically connecting said first-named indicating means with said onefixed contacts of said first and second pairs of fixed contacts, andhaving another portion thereof electrically connecting said source ofelectrical energy with said other fixed contacts of said first andsecond pairs of fixed contacts, said second fluid pressure conditionindicating means being energized by said source of electrical energythrough said switch means and said first-named and said second-namedelectrical lead means when pressure at or above said predeterminedpressure is received by either or both of said first and second pressureresponsive members to move either or both of said first and secondmovable contacts into engagement with the other of said pair of fixedcontacts associated therewith, the energization of said second fluidpressure condition indicating means indicating the condition whereinpressure exists at or above said predetermined minimum pressure in atleast one of said vehicle brake actuating circuits.
 2. In a brake systemhaving a first fluid circuit and a second fluid circuit for actuatingbrakes connected to said circuits, each of said fluid circuits having abrake system operating condition wherein the fluid circuits arepressurized with brake applying pressure and having a brake releasedcondition in which the circuits are not pressurized, a brake systempressurization condition warning system comprising: first and secondbrake system operating condition sensors each including switch meansopened and closed in accordance with the operating conditions sensed,said sensors respectively sensing the presence and absence of the firstand second brake circuit pressurization conditions, first warning meansactuated by at least one of said system operating condition sensorsthrough said switch means by the presence of brake actuating pressure inat least one of said fluid circuits and sensed by at least one of saidsensors, and second warning means actuated through a series connectionformed through said switch means of both said first and second sensors,said series connection being established by the presence of the brakesystem operating condition in one of said circuits and the absence ofthe brake system operating condition in the other circuit asrespectively sensed by said first and second sensors when the brakesystem is activated to operate the brakes connected to both fluidcircuits and one of said fluid circuits is not pressurized.
 3. The brakesystem condition warning system of claim 2, said first and second sensorswitch means respectively comprising a first switch and a second switch,each of said first and second switches having: first and second andthird contacts and means biasing said third contact into engagement withsaid first contact, said first and second sensors respectively furtherincluding first and second pressure responsive means respectively fluidconnected with said first and second fluid pressure actuated brakecircuits and actuatable upon pressurization of the associated fluidpressure actuated brake circuit to move said associated third contactfrom engagement with said associated first contact to engagement withsaid associated second contact, a source of electrical energy and meansconnecting said second contacts thereto, means connecting said thirdcontacts to said first warning means, and means connecting said firstcontacts to said second warning meaNs.